It's an old project from the times then I've been learning Ruby. I've used it in one research project as sofisticated makefiles.
listo is a project description and configuration utility like cmake or qmake. It can generate Visual Studio project and solution files and also qmake files for cross-platform build.
listo templates used to describe general definitions which similar for all subprojects
These files interpreted by listo core. They may have templates and projects definitions.